How do you fix a broken spring?

A broken garage door spring cannot be repaired and must be replaced. The safe sequence is the same regardless of the type. First, unplug the opener so it cannot try to lift the unbalanced door. Pull the red emergency release cord to disconnect the trolley from the door. Clamp the door fully closed with vice grips on the tracks just above the bottom rollers so it cannot fall. For extension springs, unhook the safety cable, disconnect the spring at the pulley, then install a matching new pair. For torsion springs, you need correctly sized winding bars to unwind the broken spring before installing new ones, which is dangerous DIY work. Always replace both springs together, even if only one broke.